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Baseline assessment and analysis of fish, macroinvertebrates and herpetofauna in the Otter Creek coal tracts area of Powder River County

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Baseline assessment and analysis of fish, macroinvertebrates and herpetofauna in the Otter Creek coal tracts area of Powder River County


Published 2012
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Cover title

"January 2012"

Includes bibliographical references (pages 25-26)

Introduction -- Methods -- Results -- Conclusions -- Site Photos -- Literature Cited -- Appendix A. Fish data and IBI metric calculations collected from Otter Creek Project Sites -- Appendix B. Macroinvertebrate taxa list, abundance, and metrics for the 15 collection sites

We summarize the first year of baseline surveys for the Aquatic Assessment of Fish, Macroinvertebrates, and Herpetofauna in the Otter Creek coal tracts area. Project goals were: 1) to conduct standardized surveys and collect baseline information on the aquatic and riparian communities occurring in Otter Creek and three tributaries (seasonally and spatially oriented) prior to coal development, 2) to assess aquatic community integrity and condition by interpreting key indicators recorded at sites using standardized protocols and biotic thresholds, and to compare these against reference condition standards. These data collected represent predevelopment (i.e. pre-impact, BACI design) conditions at the local reach scale. Habitat assessments, herpetofauna, macroinvertebrate and fish surveys were performed seasonally at three predetermined mainstem Otter Creek reaches (control, impact and downstream) and three tributaries coinciding with established surface water quality stations during 2011. Additionally, we added fish sampling visits to Otter Creek Impact #2 (upstream of the Threemile Creek confluence) because Threemile Creek remained dry during all visits. In total, we performed 15 surveys for fish during the visits: 11 at four mainstem Otter Creek reaches and four surveys at two tributary streams. Fifteen macroinvertebrate samples were collected during the visits; neither taxa survey was conducted at Threemile Creek in any season due to lack of surface water present. All six a priori stream reaches were visually surveyed for amphibians or reptiles during all visits. Biological community integrity was calculated for 15 fish surveys using Fish Integrated Biotic Indices (IBIs) and Observed/Expected Models (O/E), while the 15 macroinvertebrate samples were assessed with Montana DEQs multimetric indices (MT MMI). Habitat Evaluations. Of the seven sampling reaches evaluated in the study area, we found three in Proper Functioning Condition (PFC) with a stable trend and four were Functional at Risk (FAR). Reasons that sites ranked FAR were likely due to anthropogenic habitat alteration by cattle (Home Creek {Otter_1A and Threemile Creek {Otter 3m}) or stream manipulation (Otter Creek JTTrussler and Otter Creek #16). Highest site integrity scores using both the BLM Habitat and PFC Assessment methods were recorded at the Otter Creek sites #23 (Tenmile Creek) and #22 (control- Denson reach). Sites with lower habitat scores were structurally degraded predominately by cattle use and had high associated Livestock Use Indices (LUI) (Home Creek, Threemile and Otter Creek #16-fall). Point conductivity measurements recorded at all Otter Creek mainstem sites across most seasons were above the threshold for impairment levels (>500us, DEQ 2006), and Home Creek site 1A had visible signs of natural gas seepage from the sediments. Macroinvertebrate Communities: Overall, 104 unique macroinvertebrate taxa were reported from the 15 macroinvertebrate assessment samples. One known Montana species of concern (SOC), the mayfly, Caenis youngi was collected in fair numbers at the control site, Otter Creek #22. Average macroinvertebrate taxa richness per site was 29.5 and the highest taxa richness was 41 taxa reported at the Otter Creek JT site. Using the Montana DEQ macroinvertebrate multimetric index (MMI), four of the five sites (12 of 15 samples) were ranked non-impaired (good to excellent biological integrity), while all three samples from Tenmile Creek were ranked marginally impaired. Stream sites that maintained flowing, connected water scored higher with the MMI than sites withinterrupted pool areas. Overall, mainstem sites evaluated in the Otter Creek study received significantly higher macroinvertebrate MMI scores than those in the tributaries (T-test, p <0.01). MMIs did not significantly differ on Otter Creek mainstem Pre-Impact Control, Impact or Downstream Sites (T-test, p >0.05), despite the fish communities reflecting a decrease in biotic integrity. Fish Communities. Overall, nine fish species (five native/four introduced) were identified from 37,679 individuals collected from 15 site visits (Table 4). One potential species of concern (PSOC), the brassy minnow, was collected at five of six sites. Average fish species per Otter Creek mainstem site across all seasons was 6.5 (± 0.8 SE), while the tributary sites averaged 1.75 species (Table 4). All fish presence sites also reported at least one species of amphibian. Lake chubs had the highest site occupancy rate at 93% (14 of 15 visits) followed by fathead and brassy minnows at 80% (12 of 15 visits). Fish data collected in previous years from three sites within the study area showed similar biological integrity over time. The most diverse site in the study area was Otter Creek JT site with nine species, while the most intact sites were Otter Creek Site #22 at Densons (four native) and the Tenmile Creek spring survey (two native spp.). Using Montanas Prairie Fish IBI, 9 of the 15 fish sites were ranked non-impaired (good biological integrity), two were slightly impaired (moderate integrity) and four were moderately impaired (poor biotic integrity). Fish IBIs decreased going downstream on Otter Creek, and the Pre-Impact Control Site scored significantly higher than Impact or Downstream sites (T-test, p <0.05). Amphibian and Reptile Incidentals. Eight herpetofauna species were observed, collected in dipnets/seines or incidentally recorded in conjunction with the fish, habitat and macroinvertebrate surveys. We reported four amphibian species, of which, Woodhouses Toad (Bufo woodhousii) had the highest site occupancy, occurring at six of seven sites, followed by the Northern Leopard Frog (Rana pipiens) and Tiger Salamander (Ambystoma tigrinum) recorded at five and four sites, respectively. Boreal Chorus Frog (Pseudacris maculata) was detected at three sites during the spring visits only. We also recorded four reptile species (in order of site occurrence): Western Rattlesnake (Crotalus viridis), Painted Turtle (Chrysemys picta), Terrestrial Garter Snake, (Thamnophis elegans) and Snapping Turtle (Chelydra serpentine) (SOC). Conclusions. The aquatic community sampling sites chosen for pre-impact baseline data were representative of the range of stream classes found in the Otter Coal Tracts project area: Ephemeral, Intermittent and Perennial Prairie Streams. Despite this having been an unusually high water year for the region, stream communities that we sampled encompassed the range of expected species to occur in these stream types. Biotic integrity of sites was initially higher in the upstream control reaches of Otter Creek. One extraordinary finding was the high density and large biomass of fish inhabiting the stream reach below Truslers Ranch road crossing (20,000 fish in the 300 m reach fall survey, 15 fish/m2); this was most likely an artifact of the impassible culvert located here and the fish stacking up downstream of this barrier. Density dependent fish anomalies (lesions and parasites, i.e., yellow grub and anchorworm) were prevalent at this site, indicating the fish were likely experiencing stress from overcrowding. Benthic macroinvertebrate densities at this site were low, but, more diverse than other sites, indicating that the fish may have been consuming large portions of the available insect production, having a topdown community effect


Volume 2012
Publisher [Helena, Montana] : Montana Natural Heritage Program
Year 2012
Pages 30
Language English
Book contributor Montana State Library
Contributor usage rights See terms
Collection MontanaStateLibrary

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